Aircraft flasher unit

ABSTRACT

Apparatus is disclosed which provides for the pulsing of a plurality of high intensity white lights, which lights are synchronized to flash simultaneously, and during the off period of navigation lights already installed on the airplane. Each high intensity light is controlled by a transistorized circuit coupled to the power supply lead which supplies the navigation light. Said circuit charges two storage capacitors and holds the charge on same during the on period of the navigation lights. During the off period of same, a short circuit is presented, causing a discharge of one of the capacitors, which acts to trigger the high intensity light, the burst of light being energized by the discharge of the other capacitor.

O United States Patent [151 3,676,736 stams1 July 11, 1972 [s41 AIRCRAFTFLASHER UNIT 3,526,821 9/l970 Thomas ..315/24! R x [72] Inventor: RobertL. Shier, Rydal, Pa. Primary Examiner Mfi ed L Brody [73] Assignee:Physitech, lne., Willow Grove, Pa. Attorney-Paul & Paul [22] Filed: June6, 1969 [57] ABSTRACT [211 App! Apparatus is disclosed which providesfor the pulsing of a plurality of high intensity white lights, whichlights are [$2] U.S. Cl. ..3l5/24l R, 240/7], 3l5/24l S, symh qnizgd toflash simultaneously and during the off 340/25 period of navigationlights already installed on the airplane. [51] Int. Cl ..B64d 47/06 Eachhigh intensity m is Conn-oped by a transismfized ch" [58] Field oISearch,.3l5/24l R,24l S;340/2$; cu coupled to the power supply had whichsupplies the 240/7? navigation light. Said circuit charges two storagecapacitors and holds the charge on same during the on period of the [56]References Cited navigation lights. During the off period of same, ashort circuit TED STATES PATENTS is presented, causing a discharge ofone of the capacitors, UNI which acts to trigger the high intensitylight, the burst of light 2 Tyrwhltt Cl energized the of [he omercapacitor 3,031,645 4/1962 Koontz ..340/25 3,5l9,984 7/1970 Zychal..3l5/24lRX PATENTEDJUL 11 I972 I 3.676.736

mm m 2 INVENTOR. ROBERT L. STARER ATTORNEYS.

PKTENTEDJUI 1 i 1972 SHEET 2 0f 2 INVENTOR.

ROBERT l STARER WCM ATTORNEYS.

AIRCRAFT FLASl-IER UNIT BACKGROUND OF THE INVENTION l Field of theInvention This invention lies in the field of aircraft navigationlights, and more particularly in the field of high intensity aircrafinavigation lights.

2. Description of the Prior Art For nighttime flying, aircraft areequipped with navigation lights which ordinarily present a steady lightoutput, and which are generally placed on the tips of the wings and onthe tail of the aircraft. It is highly desirable to have additional highintensity navigation lights which transmit a short impulse of highintensity light energy. The desirability of such lights lies in thepenetrating characteristic of such high intensity white light. The highintensity burst of white light will carry with it an appreciably flatspectrum of frequencies, with the result that even if meteorologicalconditions filter out a segment of such frequencies, a portion of thelight will nonetheless be propagated through the atmosphere. For thisreason, it is particularly desirable to have such high intensitynavigation lights when flying in inclement weather or other conditionswhere the field of vision is appreciably reduced. Where a plurality ofhigh intensity navigation lights, commonly called strobes, are utilizedon an aircraft, it is required by a regulation of the FAA that suchstrobes be synchronized to flash simultaneously.

Such high intensity navigation lights are commercially available and arein use on many aircraft. However, they present a serious drawback forthe aircraft which is already equipped with the navigation lights, butnot with the high intensity navigation lights. The commerciallyavailable units require independent wiring from the aircraft powersupply out through the wings to the wing tips where the lights will beplaced. Further, in order to synchronize the newly installed strobes, itis necessary to install a switching unit in a control area of theaircrafi which operates on the power supply such as to give a pulsedpower supply which is coupled to the strobes which are wired inparallel. In present commercial units, then, wires must be run from thecenter of the aircraft through and out to the end of each aircraft wing.This presents a substantial installation cost which causes the additionof high intensity navigation lights to be so expensive as to beeconomically unfeasible for many aircrafl.

SUMMARY OF THE INVENTION Apparatus is d'mclosed which provides a systemfor pulsing high intensity navigation lights for use on airplanes, whichlights are synchronized to flash simultaneously and during the ofi'period of the standard navigation lights, the apparatus requiring noindependent power supply. The lights are coupled to and driven by thevoltage supply which is delivered to the locations of the alreadyinstalled navigation lights. The apparatus thus does not require anyindependent power supply, and particularly obviates any additionalwiring from the point of installation to the location of the aircraftpower supply. The voltage delivered to the standard navigation lights iscaused to alternate periodically between a nominal positive supply valueand zero. When said power supply voltage is at its non-zero value, itpowers a step-up voltage circuit which generates a high voltage which inturn charges two capacitors, said charge to be used to trigger andenergize the high intensity light. At the same time, the supply voltageis impressed on an electronic switch circuit which operates to presentan open switch to the capacitors, thereby preventing their discharge.When the power supply voltage goes to zero, the switch circuit presentsa closed switch, thereby enabling discharge of the capacitors, whichdischarge is caused to trigger and energize the high intensity light.The light is maintained in the on state for a brief period, after whichthe voltage supply becomes non-zero again, and the cycle repeats itself.

Accordingly, it is the primary object of this invention to provide ahigh intensity navigation light apparatus which permits the installationof high intensity navigation lights on aircrafi without requiring anyadditional wiring from the location of such lights to the power supplyof the aircraft.

It is a flrrther object of this invention to provide apparatus forsynchronizing high intensity navigation lights on an aircraft in themanner prescribed by Federal regulations.

It is a further object of this invention to provide high intensitynavigation light apparatus utilizing the same power supply wiring as isinstalled for driving standard navigation lights.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of the wiringfor both the standard navigation lights and the high intensitynavigation lights.

FIG. 2 is a schematic diagram of the switch installed at the location ofthe aircrafl power supply with which to control the operation of thenavigation lights.

FIG. 3 shows a preferred embodiment of the high intensity navigationlight pulsing circuit.

DETAILED DESCRIPTION OF THE DRAWINGS FIG. 1 sets forth the overallwiring diagram showing the distribution of power to both the standardnavigation lights and the strobes. Transmission leads 1 are presumed tohave been previously installed for operau'on of the standard navigationlight 2. The strobe lights 10, which are to be added to the aircraft,are located at or near the positions of the standard navigation lights2, i.e., at the wing tips and on the tail. The power source 20 iscoupled through a switch 21, the navigation lights and the strobes allbeing connected in parallel between the output of switch 21 and aircraftground.

FIG. 2 shows in detail the operation of switch 21. The power supplyvoltage, V,, is applied to a three-position switch. If steady power isdesired to the standard navigation lights, without any activation of thestrobes, this switch is placed on position A. If it is desired to haveno power transmitted to any of the lights, the switch is placed onposition 8. If strobe operation is desired, the switch is placed onposition C, in which case the voltage V, is coupled through aconventional modulator, or make-break circuit, which produces an outputthat is alternately zero volts and V,.. The value of V, during itsalternate non-zero periods is typically +6 volts, but it could bedesigned to be any value. The make-break circuit can be set so that thenavigation lights barely flick 05, such as would occur if the zeroduration were approximately l0 milliseconds. In this manner, thenavigation lights would have the appearance of being continuously on.However, as will be seen below, even such a small off duration would besufficient to trigger the strobe lights, which would flashsimultaneously. The output terminal of switch 21 is coupled through tothe navigation lights 2, through leads 1.

Turning now to the circuitry which controls the high intensitynavigational lights, it is seen that voltage V, is coupled to oscillator4, which is a conventional Hartley oscillator utilizing one transistor.Such oscillator, of course, develops an output signal only when thevoltage c cis applied to it, this being only when navigation light 2 ison, in the embodiment illustrated. The output of such oscillator iscoupled through transformer 5 to winding 16, the trand'ormer providing astepped up voltage across winding 16 which is typically in the order of300 volts peak voltage. This voltage is halfway rectified through diodepair 6, causing capacitors 7 and 8 to charge up to a voltage ofappreciably the peak voltage appearing across coil 16. Capacitor 7charges directly through diode pair 6 and consequently reaches fullcharge in a very short time period. Capacitor 8 charges through a largeresistance 9 which is typically of approximately 3.3 megohnu. The timeconstant for charging capacitor 8 is measured appreciably by the valueof large resistance 9 multiplied by capacitor 8, which time constant islimited only insomuch as it must be lea than the time period duringwhich lamp 2 is on. In the typical case, capacitor 8 is 0.01microfarads, which combined with a large resistance 9 value of 3.3megohms yields a time constant of 0.033 seconds, well within the typicalon time period of navigation light 2.

Power supply voltage V is also connected through a resistor diodecombination 17 to a capacitor 12, and through a re sistanee 18 to atransistor 1 I. With V at its non-zero value of typically +6 volts,transistor 11 is driven into saturation, in which state its collector isapproximately 25 millivolts above ground. The collector lead oftransistor 11 is coupled directly to the base terminal of transistor 13,a power transistor requiring approximately 0.5 volt bias to switch iton. Consequently, transistor 11 acts as a clamp to hold transistor 13 inan of! con dition, while capacitance 12 charges to slightly less than VIt is to be noted that transistor [3 is a power transistor capable ofholding up to 500 volts from collector to emitter, and is not turned onby the voltage on capacitor 8. Thus, the quiescent condition at the endof the portion of the voltage cycle wherein V is non-zero is manifestedby a stored charge on capacitor l2, transistor 13 acting as an openswitch preventing flow through transformer 14, and a stored charge onboth capacitors 7 and 8.

High intensity navigation light 10 is typically a xenon tube designed toradiate short time duration pulses of high intensity light. It could beany commercially available high intensity flash-type bulb. In order tocause the light 10 to flash, a trigger pulse of or in excess of athreshold value must be applied to the xenon tube trigger input terminal18, causing said xenon tube to ionize. Once having ionized, the tubewill continue to conduct and transmit light so long as a thresholdcurrent is maintained through same. Such current would, in the tubeillustrated, pass from terminal 23 to ground terminal 19. During thestate of the circuit thus far described, the voltage developed atterminal 18 is insufficient to trigger the tube into conduction.Ionization is induced only by a high voltage at terminal 18, the levelof which depends upon the type tube selected. A large voltage will begenerated at terminai 18 only by a transient current through transformer14 producing a variation of current with respect to the time sufiicientto in duce a large voltage in coil 22. Since capacitor 8 is chargingcontinuously and relatively slowly through large resistor 9, no largevoltage induction will be generated during the time period that V, isnon-zero.

When switch 2i breaks connection to power supply 20, such that lead Icarries no voltage, transistor ll is immediately taken out of itssaturation state, and becomes an open circuit from collector to ground.The charge stored in capacitor 12 cannot leak 05 through resistor diodecombination 17, the diode being back-biased, but can discharge directlyto ground through transistor 13 which is then forward biased tosaturation by the large positive voltage impressed on its base by thecharge on capacitor 12. With transistor 13 switched on such that itappears as an effective short to ground from collector to emitter, thecharge on capacitor 8 can discharge directly through transformer 14 andtransistor 13 to ground. There being very little resistance in thispath, this discharge is very rapid, thereby inducing a high voltageacross coil 22 of transformer l4. Said high voltage is impressed uponterminal 18, thereby firing the xenon tube 10. Once fired (ionized), thelarge charge on capacitor 7 will discharge through tube 10, therebysupplying the energy for the high intensity burst of light. The chargeon capacitor 7 can discharge only through xenon tube 10, as the tube isan appreciably small resistance to ground compared to large resistance9, or the back biased diode pair 6. Further, the time constantassociated with this discharge is quite small. It will, of course, bedetermined by the choice of tube 10, but for most tubes commerciallyavailable, the discharge will be substantially complete in a matter ofmilliseconds. A diode I5 is placed in the circuit in parallel withtransistor 13 to dampen oscillators.

Thus, at the moment that navigation light 2 turns off, the highintensity navigation light is triggered and emits a high energy burst oflight for a time duration well within the period of time that thenavigation light is off. It is to be noted that during this time,oscillator 4 is also off, there being no need to induce voltage acrosscoil 16 during this period. At the termination of the off period for thenavigation light, V, is again applied both to the navigation light andthe high intensity light circuitry, at which time the cycle repeatsitself, i.e., the oscillator turns on, capacitors 7 and 8 charge upfully, transistor 11 becomes a closed switch, and transistor 13 becomesan open switch.

Although the foregoing has described a particular embodiment of myinvention, it is noted that many modifications and changes can be madewithout departing from the spirit and scope of the invention. Oscillator4 can be of any conventional design, and can be designed to operate withvirtually any impressed voltage. Although the use of a transformer toprovide a stepped-up voltage is a very simple and stable method ofachieving such high voltage, other conventional circuitry, such aschoppers, could be utilized to obtain a stepped-up voltage with which tocharge capacitors 7 and 8. Similarly, many variations of the switchingcircuit 24 are possible. Further, although the high intensity light hasbeen illustrated as a xenon tube, any tube or lamp capable of emittingshort bursts of high intensity light would be suitable. The circuitryfor triggering and driving such light would necessarily be determined bythe characteristics of said light. For instance, if the light chosenwere to ionize or otherwise trigger at a relatively low voltage levelacross terminals 23 and 19, the stored voltage across capacitor 7 wouldbe lowered accordingly. Further, in the event that it was desired to usea two terminal light, the triggering circuit would be modified inaccordance with the triggering characteristics of such two terminallight. It is anticipated that said high intensity navigation lights willbe placed wherever the navigation lights are located, this typicallybeing on the wing tips and on the tail.

What is claimed is:

1. A system on an aircraft for synchronizing a plurality of highintensity navigation lights, to be operated with already installednavigation lights and utilizing the power supply provided to saidnavigation lights, comprising:

a. aircraft power supply means to generate a periodic on-off voltagesignal;

b. transmission means, transmitting said voltage signal to the locationof said navigation lights;

c. oscillator means, coupled to and driven by said transmitted voltagesignal;

d. stepup voltage means, coupled to the output of said oscillator means,to generate a high voltage;

e. charge storage means, coupled to and driven by said stepup voltagemeans;

f. electronic switch means, the input of which is coupled to and drivenby said transmitted voltage signal;

g. transformer means, coupling said charge storage means to saidelectronic switch means;

h. high intensity light means, having a trigger input terminal;

and,

i. coupling means, coupling said high intensity light means to saidcharge storage means and to said transformer means.

2. The invention as described in claim 1 wherein said electronic switchmeans include:

a. a first transistor, having its base coupled to said transmittedvoltage signal;

b. a second transistor, having its base coupled to the collector of saidfirst transistor;

c. a capacitor, coupled resistively to the base of said secondtransistor;

d. resistor-diode coupling means, coupling said transmitted voltagesignal to said capacitor; and,

e. diode means in parallel with said second transistor.

3. The invention as described in claim 2 wherein said charge storagemeans are comprised of:

a. diode means to halfway rectify said high voltage;

b. first capacitor means, coupled to and charged directly through saiddiode means;

c. second capacitor means in series with a large resistor, the

combination driven by said diode means.

4. The invention as described in claim 3 wherein said transformer meansconsists of a transformer coil which is coupled at a center tap to thehigh voltage side of said second capacitor means, one end of which iscoupled to the output of said electronic switch means, and one end ofwhich is coupled to the trigger input terminal of said high intensitylight means.

5. A system on an aircraft for flashing a plurality of high intensitynavigation lights, said flashing to be synchronized, and for controllingthe operation of navigation lights, comprising:

a. switching means, to control the mode of operation of said highintensity navigation lights and said navigation lights;

b. voltage supply means, which couple to and drive said high intensitynavigation lights and said navigation lights;

c. electronic switch means;

d. high intensity light means;

e. charge storage means, coupled to said high intensity light means, toprovide a short duration, high intensity discharge through same when itis triggered;

f. trigger means, to trigger said high intensity light means;

g. coupling means, coupling said alternating voltage supply means tosaid electronic switching means and said charge storage means; and,

h. said electronic switching means cooperating with said trigger meansand said charge storage means to cause said high intensity light meansto flash during the alternate time periods that said navigation light isturned off.

6. The invention as described in claim 5 wherein said electronic switchmeans include:

a. a first transistor, having its base coupled to said transmittedvoltage signal;

b. a second transistor, having its base coupled to the collector of saidfirst trarlistor;

c. a capacitor, coupled resistively to the base of said secondtranabtor;

d. resistor-diode coupling means, coupling said transmitted voltagesignal to said capacitor; and,

e. diode means in parallel with said second transistor.

7. The invention as described in claim 6 wherein a. said charge storagemeam include an oscillator, the output of same being transformer-coupledto obtain a stepped-up voltage, diode rectifier means driven by saidstepped-up voltage to provide a rectified voltage, and a first highvoltage storage capacitor driven by said rectified voltage to accumulatea large stored charge,

b. which stored charge discharges through said high intensity lightmeans when same is triggered to a conducting state.

8. The invention as described in claim 7 wherein said trigger meansinclude a second high voltage storage capacitor coupled to said dioderectifier means through a resistor, and a transformer, said transformerbeing coupled a. at a center tap to said second high voltage storagecapacib. at one end thereof to the high intensity light means, and

c. at the other end thereof to said electronic switch means,

whereby to trigger said high intensity light means into a conductingstate when said electronic switch means presents an effective shortcircuit to aircraft ground.

6 U I I UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,676,736 Dated Julv 11, 1972 Inventor(s) Robert L. Starer It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

line 57, after "voltage, "c cis" should be Column 2,

Signed and sealed this 17th (19.5 of October 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents USCOMM-DC 60376-900 FORM PD-IOSO (10-69) a n4, sovnmunr mannaomcl nu o-au-sa

1. A system on an aircraft for synchronizing a plurality of highintensity navigation lights, to be operated with already installednavigation lights and utilizing the power supply provided to saidnavigation lights, comprising: a. aircraft power supply means togenerate a periodic on-off voltage signal; b. transmission means,transmitting said voltage signal to the location of said navigationlights; c. oscillator means, coupled to and driven by said transmittedvoltage signal; d. step-up voltage means, coupled to the output of saidoscillator means, to generate a high voltage; e. charge storage means,coupled to and driven by said step-up voltage means; f. electronicswitch means, the input of which is coupled to and driven by saidtransmitted voltage signal; g. transformer means, coupling said chargestorage means to said electronic switch means; h. high intensity lightmeans, having a trigger input terminal; and, i. coupling means, couplingsaid high intensity light means to said charge storage means and to saidtransformer means.
 2. The invention as described in claim 1 wherein saidelectronic switch means include: a. a first transistor, having its basecoupled to said transmitted voltage signal; b. a second transistor,having its base coupled to the collector of said first transistor; c. acapacitor, coupled resistively to the base of said second transistor; d.resistor-diode coupling means, coupling said transmitted voltage signalto said capacitor; and, e. diode means in parallel with said secondtransistor.
 3. The invention as described in claim 2 wherein said chargestorage means are comprised of: a. diode means to halfway rectify saidhigh voltage; b. first capacitor means, coupled to and charged directlythrough said diode means; c. second capacitor means in series with alarge resistor, the combination driven by said diode means.
 4. Theinvention as described in claim 3 wherein said transformer meansconsists of a transformer coil which is coupled at a center tap to thehigh voltage side of said second capacitor means, one end of which iscoupled to the output of said electronic switch means, and one end ofwhich is coupled to the trigger input terminal of said high intensitylight means.
 5. A system on an aircraft for flashing a plurality of highintensity navigation lights, said flashing to be synchronized, and forcontrolling the operation of navigation lights, comprising: a. switchingmeans, to control the mode of operation of said high intensitynavigation lights and said navigation lights; b. voltage supply means,which couple to and drive said high intensity navigation lights and saidnavigation lights; c. electronic switch means; d. high intensity lightmeans; e. charge storage means, coupled to said high intensity lightmeans, to provide a short duration, high intensity discharge throughsame when it is triggered; f. trigger means, to trigger said highintensity light means; g. coupling means, coupling said alternatingvoltage supply means to said electronic switching means and said chargestorage means; and, h. said electronic switching means cooperating withsaid trigger means and said charge storage means to cause said highintensity light means to flash during the alternate time periods thatsaid navigation light is turned off.
 6. The invention as described inclaim 5 wherein said electronic switch means include: a. a firsttransistor, having its base coupled to said transmitted voltage signal;b. a second transistor, having its base coupled to the collector of saidfirst transistor; c. a capacitor, coupled resistively to the base ofsaid second transistor; d. resistor-diode coupling means, coupling saidtransmitted voltage signal to said capacitor; and, e. diode means inparallel with said second transistor.
 7. The invention as described inclaim 6 wherein a. said charge storage means include an oscillator, theoutput of same being transformer-coupled to obtain a stepped-up voltage,diode rectifier means driven by said stepped-up voltage to provide arectified voltage, and a first high voltage storage capacitor driven bysaid rectified voltage to accumulate a large stored charge, b. whichstored charge discharges through said high intensity light means whensame is triggered to a conducting state.
 8. The invention as describedin claim 7 wherein said trigger means include a second high voltagestorage capacitor coupled to said diode rectifier means through aresistor, and a transformer, said transformer being coupled a. at acenter tap to said second high voltage storage capacitor, b. at one endthereof to the high intensity light means, and c. at the other endthereof to said electronic switch means, whereby to trigger said highintensity light means into a conducting state when said electronicswitch means presents an effective short circuit to aircraft ground.